Welding is always a better option to ensure less or no leaking. I think though only certain parts of the exahust can be welded together prior to installation as there is not a lot of room for the rear header (depending on install method). I think the consensus is that for SD's you need better clamps, maybe some RTV and a better flex section. SD downpipes don't appear to be as straight at some of us woulk like so you could mod that section too.